sobibneb



(No Model.) Q 2 Sheets-Sheet 1.

G. E. SGRIBNER.

MULTIPLE SWITCH BOARD SYSTEM.

No. 442,145. Pa tented Dec. 9, 1890.

TIZQI'JJ. [Wen/b7",

(No Model.) 2 SheetsSheet 2.

G. E. SGRIBNER.

MULTIPLE SWITCH BOARD SYSTEM.-

No. 442,145. Patented Dec. 9, 1890.

B MMQ IlNiTen I STATES PATENT CTTTCE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE IVESTERN ELECTRIC COMPANY, OF SAME PLACE.

MULTIPLE-SWITCH-BOARD SYSTEM.

SPECIFICATION forming part. of Letters Patent No. 4: i2,145,dated December 9, 1890.

Application filed November 23, 1888. Serial No. 291.659. (No model.)

To all whom it may concern.-

Be it known that 1, CHARLES E. Scanzxnn,

a citizen of the United States, residing at Chicago, in the county of Cook and State of lili- 5 nois, have invented a certain new and useful Improvement in Multiple-Switch-Board Systems, (Case 176,) of which the following is a full, clear, concise, and exact description,ref erence being had to the accompanying drawings, forming a part of this specification.

Hy invention relates to that class of in ultiple-switch-board circuits in which metallic telephone-lines and singlecircuit or grounded lines are connected with the same exchange.

I11 my Case 175, filed October 15, 1888, Serial No. $8,144), I have described and claimed operators apparatus and circuits, so arranged as to avoid the effects of induced currents from other circuits in connection with a uni form test for all the lines. \Vhen two lines are looped together in metallic circuit, the

opposite sides of the metallic circuit thus formed are connected to ground on one side through aself-induction coil and on the other side through a self-induction coil and testbattery. I11 my said case, however, I found it necessary to provide a special plug for making the tests, since the regular connecting-plug of each pair could not be used for testing in case a metallic-circuit subscriber called for a singlecircuit subscriber, as in such case there would be a false signal resulting from the circuits connected with the test-battery.

My invention herein is designed to avoid the necessity of using a special test-plug. This I accomplish by means of a condenser placed in the circuit of the operators telephone-set and a proper switching device. The telephone-circuits and the subscribers outfits may be the same as illustrated in said prior application, and a self-induction device corresponding in capacity to that of the telephone proper may be used to preserve the balance when the telephone is connected with the circuit. The different strands of the connecting-cords are also connected each through different self-induction coils to ground, and a test-battery which may be common to a large number of cords is provided in one of said branch ground connections, the same as described in my prior application.

The loop-switch which I preferably employ is of special construction, and the circuits connected therewith are so arranged in connection with the condenser that. one loop-plug of a pair maybe used for answering any subscribers cal], while the other loopplug ot the pair may be used in testing the line called for and in making the connection therewith. The loop-plug of a pair which is connected with the calling subscribers line is sometimes spoken of as the answeringplug, while the other plugthat is, the one used to connect with the called subscribers line-is sometimes termed the connecting-plug. It is the connecting-plug that I use in testing the line called for.

When the operators telephone set. is switched into circuit of any pair of cords by means of the cam -lever, the condenser is brought in the strand connecting the tips of the cords-that is to say, in the strand which connects together the terminals of the two plugs, which are designed to be connected with the springs, respectively, of the springjack switches of any two lines with which they are connected. hen the answeringplug is inserted to connect with any calling subscribers line, a circuit is formed from the test-battery to the sleeve of said plug, and thence connection is made with the several test pieces of the line, and thence the circuit may be traced over the limb of the metallic circuit connecting with said test-pieces to the subscribers station, and thence back over the other limb of the metallic circuit to the spring of the switch in which the plug is inserted, and thence to the tip of the plug, and thence through the condenser to the tip of the answering-plug of the pair. The condenserbeing charged by the test-battery,when the connection is first made the test-battery will be shut off from the tip of the connecting-plug at the condenser. Voice-currents may, however, be sent through the condenser. Thus, by throwing the loop-key in proper position the operators telephone will be brought into circuit with the calling subscriber and the order of the calling subscriber may be received by the operator. The operator having received the order at once applies the tip of the connecting-plug to the test-piece of the line called for. As before stated, the testbattery with respect to the circuit of the calling subscribers line is shut off from the tip of the connecting-plug at the condenser. Therefore if there be no current present from some other source at the test-piece to which the tip of the plug is applied, there will be no sound heard in the operators telephone when thus connected therewith, for the reason that the operators telephone is con nected with the strand of the cord which connects to the tip of the connecting-plug at a point between the condenser and the said strand, even though the line tested were a single-wire circuit having its test-pieces connected together and through resistance to ground. Therefore the operator making the test and hearing no sound will know that the line is free. On the other hand, if the operator hears a click in her telephone when the test is made she will know that battery is connected with the test-circuit of the line called for, and this will indicate that the line is busy.

My invention is illustrated in the accompanying drawings, in which Figure 1 is a diagram illustrative of three telephone-lines two metallic and one single-connected with three different switch-boards at the central office in connection with the operators apparatus and circuits at two of the boards embodying my invention. Fig. 2 is a detail view of the circuits of a single pair of cords, the springs and contacts of the loop-switch connected therewith being shown in perspec tive. Figs. 3 and 4 are elevations of the different sides of the cam-lever loop-switch in detail.

Like parts are indicated by similar letters of reference throughout the different figures.

I will first. describe the operators apparatus, as illustrated in Figs. 2, 3, and at. The answering loop-plug a is shown inserted in a switch. The other plug 1) of the pair is shown with its pair touching a test-piece as in the act of testin The circuit between the tip of the plugs 19 and a may be traced as follows: From the tip of the plug 1) bystrand c to calling-key d, thence to contact 6 and springf of the switch, thence through the condenser g to contact h of the switch, and thence to spring 'i of the switch, and thence to the other calling-key 7c, and thence to the tip of plug a. The circuit between the sleeves of the plugs may be traced directly by strand Z. The ground branch at is permanently connected through a self-induction coil with the strand 0, while the branch n is permanently connected with the strand Z through a selfinduction coil and test-battery 0. Between the condenser g and the springf of the switch a ground circuit or branch is provided, which passes through the operators telephone, thus connecting the telephone with the strand 0 when the switch is in the position shown. From the strand Z a branch 19 connects with the contact 12 and spring 19' of the switch, spring p being permanently connected with a self-induction device 19 included in a ground circuit. WVhen the telephone is connected with strand 0, the corresponding selfinduction devicep or dummy telephone-set, as it has been sometimes called, is connected in a similar manner with the strand Z. l Vhen the leverqof the switchisthrowndown, the connections of the springs are changed, the springs f and 12 being separated from their contacts 6 19', respectively, while springt' is at the same time disconnected from its contact 7t and closed to its lowercontact g. In this manner the telephone, as well as the corresponding dummy set, may be disconnected from the strands of the cord and theportion ot' the operators telephone-circuit containing condenser 9 cut out, the circuit of cord 0, however, being completed through the clearing-out shutter contact q, and spring 1' direct. Thus when the lever is thrown down we have direct circuits through the strands of the cords, the

cord Z being, however, provided with the ground connection a through the self-induction coil and test-battery 0, while the other cord 0 is provided with the connection m through a similar self-induction coil. The calling-keys (Z 70 are of the usual construction. By depressing key at current will be sent over the circuit connected with the tip or plug 1), while on depressing key 7c current will be sent from the generator over the circnitwith which the tip of plug a may be connected. It will be seen that the switching device, operated by lever q, consists of three springs f i19 The cam at the lower end of leverq is placed in position to force the springsf and 29* away from contacts 6 and 19, respectively, and at the same time separate spring 2' from contact h and close the same upon contact 6 when the lever is thrown forward. hen the lever is up, the springs, by their own tension, are brought to the positions shown in Figs. 2, 3, and 4.

Referring now to Fig. 1, it will be seen that telephone-line 1 extends in two branches or limbs to the central office, the limb 1* being connected through the springs of the switches a' r o on the dilterent boards, and from the contact of the switch 1* through the individual annunciator r to ground. Limb r is connected with the frames or test-pieces of said switches r 1' 1- The single-wire circuit 0' extends from the subscribers station thereof through the springs and contacts of the switches r 1' r and from the contact of switch 0- through the individual annunciator r to ground. The rings or test pieces of switches 1' r r are permanently connected together by test-wire r Said test-Wire S, in-

stead of extending back tosu bscribers station, as is the case with respect to metallic circuits, is connected directly to ground through resist- The metallic circuit 9' extends ance 1' IIO from the subscribers station thereof in two branches through switches r 0- and r the same as described with respect to metallic circuit r, the individualannunciator 1' being included in the limb or branch which passes through the springs and contacts of the switches. The operators apparatus at the last board I have lettered to correspond with the lettering of Fig. 2. Similar apparatus is provided at the first board, the pair of plugs (tb being shown inserted in spring-jacks r r, respectively, to switch the telephone-lines r 4' together. The cam-lever s is thrown up and the operators telephone at the first board is disconnected from the united circuits of the two lines, while the clearing-out annunciator s is included in the circuit. The test-battery o is connected to the strand Z, which connects together the sleeves of the plugs a b. The resistance 4' in the test-circuit 1' is so great that only a small amount of current will pass from the battery 0 to ground through said resistance T. We will suppose that when two wires are thus connected upon one board one of the connectedlines is called for at another boardas, for example, at the last board. Let the signal be sent in overmetallic circuit 9* to throw down the shutter 1' at the last board, as shown. The operator, seeing the shutter of annunciatorr fall, inserts answering-plug a into the spring-jack r, and, throwin g down the lever (1, brings her telephone into circuit and is in position to receive the order. The order being received, we will say for connection with line '1', said line '2' is tested by means of the connecting-plug I) applied to the test-piece of switch 1", as shown. As line '1' is already connected at another board, the test-battery 0 will be closed to the tip of plug 1) when applied to the tip of the frame of switch 0' and the operator, listening at her telephone, will hear the sound which is due to the closing of the circuit. The circuit thus formed may be traced from battery 0 to the strand Z of the cords at the first board and thence to the sleeve of the plug a, thence to the frame of switch 0' and thence to the frame of swi ch 1*, thence to the tip of plug 1), thence to the strand 0, connecting the tips of the cords, and thence through contact eand spring f of the switch, and thence through the operators telephone to ground. The operator, listening at the telephone and hearing the sound, will know that the line tested is busy. Suppose the singlewire circuit 9- were asked for instead of the metallic circuit '2'. In this case the test would be made at switch 1" and the circuit thus formed from the test-battery might be traced to strand Z of the cords at the first board, thence to the sleeve of plug r and thence to the tip of plug 6, and thence through the strand c to key 7;, thence to contact 6, spring f, and the telephone to ground.

If the condenser g were notincluded in the circuit a false signal would be heard in the operators telephone 011 testing an idle singlecircuit telephone-line, as circuit 1- Thus, as

shown at the last board, the answering-plug a is inserted in sprin g-jack switch 0'". Tracing from battery 0, the circuit is complete to the sleeve of plug a, thence to the frame of switch 7*", and thence over circuit 2' through the subscribers station and back to the spring of switch '2'", thence to the tip of plug a, thence to spring t of the switch and contact 71, and thence through the telephone to ground. Thus, omitting the condenser, a complete cir cuit is formed from battery 0 through the operators telephone. Now on applying the tip of the connecting-plug Z) to the frame of a switch 1' of a single-circuit line, a third leg or half-connection would be formed to ground through resistance 0 The closing of this branch to ground would change the electrical condition of the telephone and causeasound therein which could not be distinguished from a true busy-signal. Thus without the condenser there would be no sure means of determining whether a single line called for by a metallic-circuit subscriber was busy.

In my prior application an extra test-plug is provided and the condenser is not used.

Each operator may have, say, fifteen pairs of connecting-cords, and consequently fifteen switches. Of those switches the diiferent springs f are connected together and to the ground branch, including the operators telephone. Spring t' is connected only to its particular strand of a pair of cords. These contacts of all of each operators switches, whatever the number may be, are connected together and to the wire connecting with one side of the condenser, as shown. Springs 19 of these switches are connected together and to the ground branch, including the dummy telephone-set 1)". Thus it will be seen that only one condenser is required for each operators outfit.

My invention admits of various modifications, which would readilysuggest themselves to those skilled in the art, and I therefore do not limit my invention to the construction shown.

IIavin g thus described my invention, I claim as new and desire to secure by Letters Pat cnt-- 1.. The combinatiomwith a metallic-circuit telephone-line connected with switches on two or more switch-boards, one branch of said metallic circuit being normally open at the central office and the other branch being normally connected through an individual annunciator to ground, of a single-wire circuit connected with switches, one on each of the switchboards, and through an annunciator to ground, the frames or test-pieces of the switches of said single line being connected together and through resistance to ground, and operators apparatus consisting of a pair of loop-plugs and the cords connected therewith, one strand of said cord being connected with a ground branch containing a self-induction coil and ex tending from the connection with said branch through one spring and contact of a switching IIO IIS

device, thence through a condenser to another ground branch containing a telephone, and thence through another spring and contact of said switching device, the other strand of said pair of cords being connected with a ground branch including a test-batteryand self-induction coil,whereby the two telephone-lines may be tested and connected together, substantially as and for the purpose specified.

2. The combination, with a metallic-circuit telephone-line connected with switches on two or more switch-boards, one branch of'said metallic circuit being normally open at the central office and the other branch being normally connected through an individual annunciator to ground, of a single-wire circuit connected with switches, one on each of the switchboards,and through an annunciator to ground, the frames or test-pieces of the switches of said single line being connected together and through resistance to ground, and-operators connecting, switching, and testing apparatus, whereby the two telephone-lines maybe tested and connected together, substantially as and for the purpose specified.

3. A metallic circuit with the answeringplug of a pair inserted in a spring-jack switch of the line upon one of two or more switchboards with which the lineis connected, the single-circuit line connected with the same switch-boards, the frames or test-pieces of the switches of said single-circuit line being connected together and through resistance to ground, the answering-plug of said pair being applied to the ring or test-piece of the switch of the single-circuit line on the same board with the switch of the metallic circuit in which the answering-plug is inserted, a test-battery connected with the strand of the'cords which unites the sleeves of the plugs, a'condenser included in the circuit of the other strand of the cords, and a telephone in a ground branch connected with said strand, the connection with the telephone being on the side of the condenser nearest the connecting-plug,whereby current from the test-batteryis prevented from passing through the test-circuit of the. single line to ground, substantially as and for the purpose specified.

In witness whereof I hereunto subscribe 5 my name this 17th day of November, A. D.

CHARLES E. SCRIBNER. Witnesses:

GEORGE P. BARTON, ELLA EDLER. 

